Cubic ferrite with a high upper frequency limit



United States Patent 3,394,082 CUBIC FERRITE WITH A HIGH UPPER FREQUENCY LIMIT Mieczyslaw Hildebrandt, Jean Nicolas, and Avnir Vassiliev, Paris, France, assignors t0 CSFCompagnie Generale de Telegraphic Sans Fl], a corporation of France No Drawing. Filed Oct. 27, 1964, Ser. No. 406,887 Claims priority, applicgastiogsyrance, Oct. 30, 1963,

1 Claim. (Cl. 252-6258) ABSTRACT OF THE DISCLOSURE The invention concerns cubic lithium ferrites used in application involving scalar permeability and defined by the formula Ml 1 X) F6203, 351 91120 ZCOO wherein:

x lies between 0 and 0.25 y lies between 0.15 and 0.6 z lies between 0.04 and 0.35

The ferrites according to the invention have a higher frequency limit than conventional ferrites.

The present invention, relates to cubic lithium ferrites.

These materials are used in applications involving scalar permeability, for example for the fabrication of magnetic cores.

Known materials of this kind have an upper frequency h, of the order of a few tens of mc./s., at which relaxation phenomena cause a rapid rise of magnetic loss and lowering of the initial permeability.

'It is an object of this invention to provide ferrites with a higher {frequency limit than conventional ferrites. The ferrites accordnng to the invention have a composition defined by the formula:

x lies between 0 and 0.25 y lies between 0.15 and 0.6 2 lies between 0.04 and 0.35.

The invention will be better understood from the following description of the method of manufacture of a ferrite.

The raw materials used are the compounds Fe O A1 0 lMn0 CO Li and C00 with a degree of purity higher than 99.5%. The compounds are proportioned by weight, crushed in distilled water for 24 hours in steel ball-mills and dried. The resulting mixture is pre-sintered at 800 C. for 2 hours and crushed once more as above. When dried, the powder is transformed to a granulate by adding by weight of aqueous polyvinyl alcohol solution. The granulate is pressed at a pressure of 1 ton 3,394,082 Patented .luly 23, 1968 "ice per cm. The resulting parts are sintered for 3 hours at a temperature T, between 1100 and 1200 C.

Of course, certain details of the process can be varied without departing from the spirit of the invention. How- 5 ever, it is to be noted that the sintering temperature is relatively critical.

It the sintering temperature is less than 1100 C., the resulting material is crumbly. If the temperature is above 1200" C., the material decomposes.

The following table shows the characteristics of the matenal obtalned, against parameters x, y and z and temperature T ,u being the initial permeability:

15 Example No. x y z T) lfr. m0./s'

What is claimed is:

1. A ferrite composition having low losses in the frequency range between 50 and 200 mc./ s. defined by the formula:

References Cited UNITED STATES PATENTS 2,958,664 11/1960 Vassiliev et a1 252-625 3,007,874 11/1961 Peyssou et a1 252-625 3,030,307 4/1962 Baird et al. 252-625 3,066,103 11/ 1962 Owen 252-625 3,072,576 1/ 1963 Greenhouse 252-625 3,232,877 2/1966 Vassiliev et a1. 252--62.5 3,245,911 4/1966 Vassiliev et al. 252-625 OTHER REFERENCES Aghajanian: High Curie Temperature Square Loop Ferrites, IBM Technical Disclosure Bulletin, page 85,

volume 4, No. 12, May 1962.

TOBIAS E. LEVOW, Primary Examiner.

R. D. EDMONDS, Assistant Examiner. 

